Circulating brain-derived neurotrophic factor, leptin, neuropeptide Y, and their clinical correlates in cystic fibrosis: a cross-sectional study

Abstract

Introduction

Cystic fibrosis (CF) involves chronic inflammation and decreased pulmonary function, which increase caloric demand. Yet, sufficient energy provision is hindered by reduced appetite and fat malabsorption. Brain-derived neurotrophic factor (BDNF), leptin, and neuropeptide Y (NPY) belong to energy balance-regulating factors. We aimed to assess their concentrations in CF patients in order to search for potential clinical correlates.

Material and methods

This was an exploratory, cross-sectional study. Patients’ weight and height Z-scores, forced expiratory volume in 1 s (FEV₁%), exocrine pancreatic status (fecal elastase-1), genotypes, and other characteristics were assessed. Serum concentrations of BDNF, leptin, NPY, IL-6, and TNF-α were measured using ELISA.

Results

The study enrolled 56 patients, of whom 29 (52%) were female and 17 (30%) were younger than 16 years. Median (1st–3rd quartile) mass Z-score was –0.85 (–1.56–(–0.36)); median FEV1 was 70.5% (45.0–89.5); 48 (86%) patients had exocrine pancreatic insufficiency and 8 (14%) diabetes. Overall, median concentrations were: BDNF: 33.91 ng/ml (26.40–40.43), leptin: 12.05 ng/ml (8.93–17.77), NPY: 2.86 ng/ml (1.75–4.42). None of these factors correlated with mass Z-score, FEV₁%, IL-6 or TNF-α. Leptin and NPY correlated negatively (ρ = –0.62, p = 3 × 10^–7); BDNF/NPY ratio was associated with leptin (ρ = 0.54, p = 2 × 10^–5), BDNF/leptin ratio correlated with NPY (ρ = 0.60, p = 1 × 10^–6). In a multivariable regression analysis NPY was weakly, but independently, associated with FEV1%, and leptin with age.

Conclusions

BDNF and leptin were not associated with weight Z-score or FEV₁%. Serum NPY concentrations seemed to be lower in CF patients with reduced pulmonary function independently of malnutrition and inflammation.